Actuator for an electrohydraulic braking system

ABSTRACT

The present invention relates to an actuator for an electro-hydraulic braking system of the ‘brake-by-wire’ type comprised of a hydraulic pressure generator or master brake cylinder and a travel simulator, with said master brake cylinder including at least one piston that is operable by an actuating pedal, and wherein a device for detecting a driver&#39;s deceleration wish is provided, said device cooperating with said piston and being at least partly arranged in a master brake cylinder housing. To optimize the assembly in terms of packaging, production costs, weight, and function, the present invention discloses that the device for detecting a driver&#39;s deceleration wish comprises an annular housing embracing the piston in a radial direction and accommodating signal receiving elements which cooperate with signal transmitting elements mounted on the piston surface.

TECHNICAL FIELD

The present invention generally relates to an actuator for anelectro-hydraulic braking system and more particularly relates to anactuator for an electro-hydraulic, ‘brake-by-wire’ braking system.

BACKGROUND OF THE INVENTION

An actuating unit of this type is generally disclosed in patentapplication DE 199 29 154.3. The special features of the prior-artactuating unit consist in that the travel simulator is provided by aresetting spring biasing the piston in opposition to the direction ofactuation, and there is a valve device which closes or opens a hydraulicconnection between the pressure chamber bounded by the piston and anon-pressurized pressure fluid supply reservoir. The mentionedpublication, however, does not provide a system for detecting a driver'sdeceleration wish.

BRIEF SUMMARY OF THE INVENTION

In view of the above, an object of the present invention is to disclosefor an actuator of the type mentioned hereinabove a device for detectinga driver's deceleration wish, with said device being optimized withrespect to packaging, production costs, weight and function.

This object is achieved by the present invention which comprises anannular housing embracing the piston in a radial direction andaccommodating signal receiving elements which cooperate with signaltransmitting elements mounted on the piston surface.

A favorable aspect of the present invention implies that the piston isguided in the housing.

In another favorable embodiment of the subject matter of the invention,the annular housing is axially preloaded in relation to the master brakecylinder housing.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a design of the actuator of the presentinvention.

FIG. 2 is a perspective cross-sectional view of the actuator of thepresent invention as shown in FIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The actuator 1 for an electro-hydraulic brake system of the‘brake-by-wire’ type, as shown in the drawing, includes a dual-circuitpressure generator or master brake cylinder 2, a travel simulator 3, andan non-pressurized pressure fluid supply reservoir (not shown)associated with the master brake cylinder 2. The master brake cylinderhousing 20 includes a radial flange 4 that is used to attach theactuator 1 to a body wall (not shown) of a motor vehicle. The attachmentin the vehicle is preferably carried out in such a way that the parts ofthe actuator arranged on the right side of flange 4 in FIG. 1 extendinto the passenger compartment, while the parts arranged on the left arearranged in the engine compartment of the motor vehicle. A flat seal 5is used to seal the flange 4 in relation to the vehicle body wall. Ahydraulic master cylinder piston 6 (FIG. 2) is operated by a piston rod7 coupled to an actuating or brake pedal (not shown) by means of a yoke8. The actuating movement of the piston rod 7 or of the master cylinderpiston 6 is sensed by means of a device for detecting a driver'sdeceleration wish, being designated by reference numeral 9.

As can be seen in FIG. 2 in particular, the device 9 for detecting adriver's deceleration wish includes an annular housing 10 that embracesthe above-mentioned piston 6 in a radial direction or, respectively, inwhich said piston 6 is guided. Disposed in annular housing 10 are signalreceiving elements 11 which, along with signal transmitting elements 12fitted to the piston surface, form a measurement system. The annularhousing 10 is axially supported, preferably under the preload of aspring 13, on a stop 14 on the master cylinder housing against which, inturn, a packing 15 bears that is used to seal the master brake cylinder2 with respect to the atmosphere. However, a design wherein the packing15 is formed integrally with the annular housing 10 is also feasible.The annular housing 10 is secured in position in the master brakecylinder housing 20 by means of a retaining ring 23 on which theabove-mentioned spring 13 is supported.

As is apparent from FIG. 2, the housing 10 includes a first cable guidepart 16 extending through an opening 17 provided in flange 4 and beingsealed in relation to flange 4 by means of a seal 18 that preferablyacts in a radial direction. This prevents the ingress of fluid into thepassenger compartment. The first cable guide part 16 is preferablyconfigured so that its contour is adapted to the contour of the sectionof the master brake cylinder housing 20 that projects into the passengercompartment so that it is e.g. able to also fulfill centering tasks inthis area.

Adjacent to the first cable guide part 16 is a second cable guide part19 that extends substantially in parallel to the master cylinder housing20 and is attached thereto by means of a fastening element 21. Anelectric interface or an electric connector part 22, respectively, isarranged at the end of the second cable guide part 19, especially in thearea of its attachment to the master cylinder housing 20. Of course,also a design is possible where the electric connector part is directlyconnected to the first cable guide part 16. A favorable design arrangesfor the annular housing 10, both cable guide parts 16, 19, and theelectric connector part 22 to be made of plastics and to have anintegral design. Additionally a modification (not shown) is possiblewherein a sealing element in the type of a pleated bellows is providedbetween the master brake cylinder housing 20 and the piston rod 7. It isparticularly expedient in this variant when the above-mentioned flatseal 5 is designed integrally with the sealing element.

1. Actuator for an electro-hydraulic braking system of the‘brake-by-wire’ type, comprising: a hydraulic pressure generator havinga working piston, a device for detecting a driver's deceleration wishwherein said device cooperates with said piston and wherein said deviceis at least partly arranged in a housing of said hydraulic pressuregenerator, wherein the device for detecting a driver's deceleration wishfurther includes a portion which adjoins an outer surface of the piston,wherein said device includes signal receiving elements which cooperatewith said piston for detecting the position or movement of the piston,wherein the device housing includes a first cable guide part extendingthrough a flange of said hydraulic pressure generator, wherein saidhydraulic pressure generator flange is used to attach the hydraulicpressure generator to a vehicle wall, wherein the housing of thehydraulic pressure generator includes said flange, wherein said flangeis sealed in relation to the vehicle wall by means of a flat seal. 2.Actuator as claimed in claim 1, herein the piston is at least partiallyguided in a housing of said device.
 3. Actuator as claimed in claim 1,wherein the device housing is a partial annulus and it is preloadedalong an axis of said piston.
 4. Actuator as claimed in claim 1, whereinthe first cable guide part extends through an opening in said flange andis sealed to the flange.
 5. Actuator as claimed in claim 4, wherein thefirst cable guide part is shaped so that a portion of its contourcorresponds to a portion of, and is cooperatively received in thecontour of the hydraulic pressure generator housing that extends into apassenger compartment of a motor vehicle.
 6. Actuator as claimed inclaim 1, further including an electric connector part provided at an endof the first cable guide part.
 7. Actuator as claimed in claim 6,further including a second cable guide part interposed between the firstcable guide part and the connector part is a second cable guide partthat extends in parallel to the hydraulic pressure generator. 8.Actuator as claimed in claim 7, wherein the second cable guide part isattached to the hydraulic pressure generator near the connector part. 9.Actuator as claimed in claim 8, wherein the hydraulic pressuregenerator, the first cable guide part, the second cable guide part, andthe connector part have an integral design.
 10. Actuator as claimed inclaim 8, wherein a housing of the first cable guide part, the secondcable guide part, and the connector part are made of plastic material.11. Actuator as claimed in claim 1, wherein the device includes ahousing, and wherein said device housing is arranged completely withinthe housing of the hydraulic pressure generator, wherein a first and thesecond cable guide part are at least partially arranged outside thehousing of the hydraulic pressure generator.
 12. Actuator as claimed inclaim 1, wherein the piston is sealed in relation to the housing of thehydraulic pressure generator by means of a packing, wherein thepackaging is integrally designed with the annular housing.
 13. Actuatoras claimed in claim 1, wherein the working piston is operable by meansof a piston rod coupled to a brake pedal and wherein a sealing elementis provided between the piston rod and the housing of the hydraulicpressure generator, wherein the flat seal is integrally designed withthe sealing element.